Our purpose is to continue the study of the use of osteochondral allograft implantation in the management of patients with skeletal defects as a result of resection for tumor or disease or traumatic loss. Experimental studies will include: 1. Continued in depth follow-up of the patients in the clinical series with special attention to the incidence, cause and nature of complications of the procedure. 2. Continued assessment of the long term effect of massive allograft implantation on the host's immune system and the effect of such alterations on the fate of the graft. 3. Assessment of the state of the graft and causes of failure by study of the graft material obtained from those patients in whom subsequent removal of the graft is required because of infection, fracture or tumor recurrence. 4. Determination by prospective and retrospective study of the effect of adjuvant chemotherapy on the rate of incorporation of the graft and the rate of the repair process. 5. Introduction of special techniques for evaluating the graft (CT, bone scanning and NMR) and the patient's performance (gait analysis) in order to more fully define the patient's status. 6. Continued study of methods to improve banking procedures with special attention to harvesting, cryopreservation techniques, maintenance of sterility, computerized record keeping and sizing, and cost containment. 7. Further development of animal models of the osteoarticular allograft procedure and utilization of these for exploration of the effects of technical improvements in fixation, cryopreservation, alterations in histocompatibility and a variety of immunosuppressive regimens. 8. Continued experimentation on techniques of cryopreservation of cartilage segments with special attention to cryopreservative agents and conditions of freezing and thawing.